When hungover, Germans speak of howling cats while Icelanders' phrase literally means to have the God of Thunder's hammers in your brain. Iberian languages refer to the undertow; apparently the land's regurgitation of water to the sea is evocative. Latin Americans show a great linguistic range in their post-bacchanal gloom, using Spanish or native words for foot, rubber, branch, guava tree, raw, cross, female persecutor and mouse.
The English term, hangover, suggests a leftover, possibly sloppy and dangly. It's hardly the most interesting description, but a bit more suggestive than the Russians' no-nonsense after the drunkenness.
The winners for most vivid word-choices, at least in my cross-linguistic survey, are the Danes, whose dreary morning-after can conjure any of the following: carpenters, crumpled, drunken illness, visited by craftsmen, the hair hurts, coordination troubles, short circuit, and, most compellingly, rats in the attic.
The poetic power on display here is impressive considering that these expressions were presumably born in that moment where we'd all like to just crawl into the corner, vomit, and switch off our brains.
Here's a full cataloging of the horrors.
A few notes:
Russians have usefully verbed "hair of the dog"; похмели́ть (pohmelit') means to serve someone alcohol in order to cure his hangover.
Russian also provides us with this wise rhyming proverb: Весело́ весе́лье — тяжело́ похме́лье (Veseló vesél'e — tjazheló pohmél'e) — fun is fun, but the hangover is serious.
The French gueule de bois (wooden mouth) uses a particularly wonderful word for mouth; a gueule usually belongs to either an animal or a jerk.
Germans use words for both howling cats and just cats for their hangovers. This feline idea of the hangover was then adopted by others, such as the Dutch and the Slovenians. But the German kater in the hangover sense originally comes not from "cat" but from the Leipzig pronunciation of Katarrh, which translates to English as pain and also catarrh, the medical term for excessive nasal and throat mucus discharge.
The Czech kocovina also means tomcat, though at least one linguist claims that its etymological meaning is riot, from the riots against an unpopular mayor named Kotz in 1848.
The Hewbrew חמרמורת (hamarmoret) is an official neologism from the Academy of the Hebrew Language, but it hasn't caught on; the English import hangover is used.
THANKS SO MUCH FOR YOUR HELP: Susanne Palm, Susanne Christensen, Ana Stijelja, Osk Sigurdardottir, Gonzalo Toloza, Nathalie Frank, Joanna Cichocka, Krista Kateneva, and the others who I'm sure I'm forgetting.
TIPSY READERS: You come from around the world and speak lots of languages, so please feel free to send in your input. The above table is a work in progress and I plan to continuously improve it. Your suggestions and corrections are welcome in the comments. Thanks!